diff --git a/Ghidra/Processors/MIPS/data/languages/mips.sinc b/Ghidra/Processors/MIPS/data/languages/mips.sinc
index f039573cf0..6f0a6d40ae 100755
--- a/Ghidra/Processors/MIPS/data/languages/mips.sinc
+++ b/Ghidra/Processors/MIPS/data/languages/mips.sinc
@@ -369,7 +369,9 @@ define register offset=0x3200 size=$(REGSIZE) [
 	HW_RES28	HW_ULR			HW_RESIM30	HW_RESIM31
 ];
 
+@ifdef ISA_VARIANT 
 define register offset=0x3F00 size=1 [ ISAModeSwitch ];
+@endif
 
 # Define context bits
 define register offset=0x4000 size=4   contextreg;
@@ -798,12 +800,14 @@ DXuPos: pos             is lsb          [ pos = lsb + 32; ]             { tmp:1
 DinsXSize: mysize         is msbd & lsb   [ mysize = msbd - lsb + 1 + 32; ] { tmp:1 = mysize; export tmp; }
 @endif
 
+@ifdef ISA_VARIANT 
 macro JXWritePC(addr) {
    ISAModeSwitch = (addr & 0x1) != 0;
    tmp:$(REGSIZE) = -2;
    tmp = tmp & addr;
    pc = tmp;
 }
+@endif
 
 # Floating point formats
 #fmt: "S"        is format=0x10   { }
diff --git a/Ghidra/Processors/MIPS/src/main/java/ghidra/program/emulation/MIPSEmulateInstructionStateModifier.java b/Ghidra/Processors/MIPS/src/main/java/ghidra/program/emulation/MIPSEmulateInstructionStateModifier.java
index 5301e44638..a47332f564 100644
--- a/Ghidra/Processors/MIPS/src/main/java/ghidra/program/emulation/MIPSEmulateInstructionStateModifier.java
+++ b/Ghidra/Processors/MIPS/src/main/java/ghidra/program/emulation/MIPSEmulateInstructionStateModifier.java
@@ -37,14 +37,17 @@ public class MIPSEmulateInstructionStateModifier extends EmulateInstructionState
 
 	public MIPSEmulateInstructionStateModifier(Emulate emu) {
 		super(emu);
-		ismReg = language.getRegister("ISAModeSwitch");
 		isaModeReg = language.getRegister("ISA_MODE");
-		if (ismReg == null || isaModeReg == null) {
-			throw new RuntimeException("Expected language " + language.getLanguageID() +
-				" to have ISM and ISA_MODE registers defined");
+		if (isaModeReg != null) {
+			ismReg = language.getRegister("ISAModeSwitch");
+			if (ismReg == null) {
+				throw new RuntimeException(
+					"Expected ISA_VARIANT language " + language.getLanguageID() +
+						" to have ISAModeSwitch register defined");
+			}
+			ISA_MODE1 = new RegisterValue(isaModeReg, BigInteger.ONE);
+			ISA_MODE0 = new RegisterValue(isaModeReg, BigInteger.ZERO);
 		}
-		ISA_MODE1 = new RegisterValue(isaModeReg, BigInteger.ONE);
-		ISA_MODE0 = new RegisterValue(isaModeReg, BigInteger.ZERO);
 
 		// These classes are defined here:
 		// ghidra/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/pcode/emulate/callother
@@ -79,6 +82,9 @@ public class MIPSEmulateInstructionStateModifier extends EmulateInstructionState
 	@Override
 	public void initialExecuteCallback(Emulate emulate, Address current_address,
 			RegisterValue contextRegisterValue) throws LowlevelError {
+		if (ismReg == null) {
+			return;
+		}
 		BigInteger isaModeValue = BigInteger.ZERO;
 		if (contextRegisterValue != null) {
 			isaModeValue =
@@ -102,6 +108,9 @@ public class MIPSEmulateInstructionStateModifier extends EmulateInstructionState
 	public void postExecuteCallback(Emulate emulate, Address lastExecuteAddress,
 			PcodeOp[] lastExecutePcode, int lastPcodeIndex, Address currentAddress)
 			throws LowlevelError {
+		if (ismReg == null) {
+			return;
+		}
 		if (lastPcodeIndex < 0) {
 			// ignore fall-through condition
 			return;